Memory elements are used in electronic systems, including volatile memories such as dynamic random access memory (DRAM), or non volatile memory such as electrically-erasable programmable read only memory (EPROM). A memory element can include a dielectric layer sandwiched between two conductor layers, acting as electrodes for the memory element.
In general, the use of electrodes with high work function can decrease leakage in high dielectric constant (e.g., high-k) dielectric stacks. Conducting materials with high work function include molybdenum dioxide (MoO2) and metallic molybdenum (Mo). However, Mo is subject to oxidation during heat treatment and/or device operation, which may promote formation of oxygen vacancies in the dielectric layer, which may deteriorate the quality of the dielectric. On the other hand, deposition of MoO2 can generate a significant amount of MoO3, which is an insulator, and can degrade the conductivity of the MoO2 electrodes.
For example, during an atomic layer deposition (ALD) of MoO2, it is often found that MoO3 forms instead of MoO2 for a wide range of experimental conditions. It is possible to convert MoO3 to MoO2 with a post-treatment in an external reducing environment. However, such post-treatment may be undesirable. For example, such a post-treatment may deteriorate the quality of the dielectric underlayer.
Therefore, there is a need for molybdenum-containing electrodes that can meet the design criteria for advanced memory devices.